The invention relates to a control wait for operating a vehicle drive and to the application of the control unit for operating an internal combustion engine or an electric machine in a motor vehicle.
As is known from German patent document DE 44 38 714 A1 the monitoring of drive control units is generally executed as a three level monitoring concept. This publication describes a method and apparatus for controlling the drive power of a vehicle using a microcomputer, with the aid of at least two mutually independent levels, a first level carrying out the control functions, and a second level carrying out the monitoring functions. A third level forms a control level that controls the monitoring level and thus the microcomputer.
One object of the present invention to provide a control unit for a vehicle drive, with improved fault detection sensitivity.
This and other objects and advantages are achieved by the control unit according to the invention, which has a first limiting device in which a provisional desired torque can be bounded above with a maximum limiting torque to a final desired torque when a detected vehicle speed is greater than or equal to a starting limiting speed. In the limiting device, this provisional desired torque can be bounded above to a final desired torque with a limiting torque dependent on the measured/manipulated variables of the accelerator pedal value sensor when the detected vehicle speed lies below a starting limiting speed.
The starting limiting speed defines a limit for the vehicle speed. From and above this starting limiting speed, the vehicle is in normal driving operation. In this range, the desired torque is bounded above by a maximum limiting torque, which prevents the drive from attempting to produce an undesirably high torque in the event of a fault.
Speeds below the starting limiting speed are ascribed to the starting range of the vehicle. In this case, the desired torque is bounded above with a limiting torque dependent on the measured/manipulated variables of the accelerator pedal value sensor. This arrangement has the advantage that the limiting torque can be selected to be lower than the maximum limiting torque. Consequently, the fault detection sensitivity of the apparatuses raised in the starting range.
In one embodiment of the invention, a limiting device is provided by which the limiting torque dependent on the measured/manipulating variables of the accelerator pedal value sensor can be bounded below with a definable minimum limiting torque. In internal combustion engines, it is necessary (for example, because of the need to adhere exhaust gas regulations) to define a lower operating limit that may not be undershot when stationary or during the starting operation. The minimum limiting torque constitutes this lower operating limit and ensures proper operation of the vehicle drive.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.